1. Field of the Invention
The present invention relates to an organic light emitting display apparatus and, more particularly, to an organic light emitting display apparatus having a hybrid structure in which a resonance pixel and a non-resonance pixel are combined with each other.
2. Description of the Related Art
Generally, an organic light emitting diode (OLED) has a structure in which an organic light emitting layer having a functional thin film type is inserted between an anode and a cathode, and generates light by recombining electrons injected from the cathode and holes injected from the anode in the organic light emitting layer.
OLED displays can be divided into a passive matrix (PM) type and an active matrix (AM) type according to a driving method thereof. In a PM type OLED display, anodes and cathodes are simply respectively arranged in columns and rows. A scanning signal is supplied to the cathode from a row driving circuit and, at this point, only one row is selected from a plurality of rows. Also, in a column driving circuit, data signals are inputted to each of the pixels. An AM type OLED display controls signals inputted to each pixel using a thin film transistor. The AM type OLED display can handle a large amount of signals, and thus is used for a display apparatus for realizing a motion picture.
Presently, in order to realize a top emission AM type OLED display having a low power consumption and a high bright room contrast ratio (CR) characteristic, an RGB independent deposition method has been widely used. In the RGB independent deposition method, patterning for each colors of light must be performed using fine metal masks. However, the RGB independent deposition method can be hardly applied to a large scale substrate due to precision problems in aligning the fine metal masks and mask sagging phenomenon as the size of masks increases. An inkjet method, which is one of the methods for forming other RGB independent light emitting layer, can be used for a large size substrate. However, the characteristics of soluble materials must be secured in advance since, presently, the characteristics of the soluble materials are inferior to those of the deposition materials. In addition, a laser induced thermal imaging (LITI) method has been used, in which a light emitting layer is independently transferred using a laser; however, this method results in a short lifetime of the OLED device.
A white OLED-color filter (WOLED-CF) method used in conjunction with a color filter in a white OLED has received much attention in consideration of processability and yield. A white OLED can be realized by forming a plurality of organic light emitting materials that respectively emit red, green and blue colors in an organic light emitting layer or by forming complementary pairs of organic light emitting materials in an organic light emitting layer. However, in the WOLED-CF method, white light must be filtered through a color filter, and thus the optical transmittance is relatively low when compared to that of the RGB independent deposition method. The WOLED-CF method has an optical transmittance with respect to white light of approximately 25%. When a resonance structure is used in the WOLED-CF method, the optical transmittance in a frontal direction can be increased approximately 30 to 50% when compared to a non-resonance case, and color reproducibility can be enlarged to be greater than 100% when compared to the national television system committee (NTSC) standard. In order to maximize the optical efficiency, an RGBW pixel structure in which a resonance RGB pixel and a non-resonance white pixel which has an optical transmittance of 100% are used can be employed. However, a display having a RGBW pixel structure that uses both the resonance RGB pixel and the non-resonance white pixel has a severe problem in changing a non-primary color due to the difference of brightness change according to the viewing angle with respect to the resonance pixel and the non-resonance pixel and, in particular, the color change according to viewing angle with respect to the white color is large. Therefore, the display can hardly be applied to actual displays.